Ocean waves have been used recreationally for hundreds of years. One of the most popular sports at any beach with well-formed, breaking waves is surfing. Surfing and other board sports have become so popular, in fact, that the water near any surf break that is suitable for surfing is usually crowded and overburdened with surfers, such that each surfer has to compete for each wave and exposure to activity is limited. Further, the majority of the planet's population does not have suitable access to ocean waves in order to even enjoy surfing or other ocean wave sports.
Another problem is that the waves at any spot are varied and inconsistent, with occasional “sets” of nicely formed waves that are sought after to be ridden, interspersed with less desirable and, in some cases, unrideable waves. Even when a surfer manages to be able to ride a selected wave, the duration of the ride lasts only a mere 2-30 seconds on average, with most rides being between 5 and 10 seconds long.
Ocean surface waves are waves that propagate along the interface between water and air, the restoring force is provided by gravity, and so they are often referred to as surface gravity waves. FIG. 1 illustrates the principles that govern surface gravity waves entering shallow water. Waves in deep water generally have a constant wave length. As the wave interacts with the bottom, it starts to “shoal.” Typically, this occurs when the depth gets shallower than half of the wave's length, the wave length shortens and the wave amplitude increases. As the wave amplitude increases, the wave may become unstable as the crest of the wave is moving faster than the trough. When the amplitude is approximately 80% of the water depth the wave starts to “break” and we get surf. This run up and breaking process is dependent on the slope angle and contour of the beach, the angle at which the waves approach the beach, and the water depth and properties of the deep water waves approaching the beach. Refraction and focusing of these waves is possible through changes to the bottom topography.
Ocean waves generally have five stages: generation, propagation, shoaling, breaking, and decay. The shoaling and breaking stages are the most desirable for rideable waves. The point of breaking being strongly dependent on the ratio of the water depth to the wave's amplitude but also depends on the contour, depth and shape of the ocean floor. In addition, velocity, wavelength and height of the wave, among other factors, can also contribute to the breaking of a wave. In general, a wave can be characterized to result in one of four principal breaker types: spilling, plunging, collapsing, and surging. Of these wave types the spilling waves are preferred by beginner surfers while the plunging waves are revered by more experienced surfers. These breaker types are illustrated in FIG. 2.
Various systems and techniques have been tried to replicate ocean waves in a man-made environment. Some of these systems include directing a fast moving, relatively shallow sheet of water against a solid sculpted waveform to produce a water effect that is ridable but is not actually a wave. Other systems use linearly-actuated paddles, hydraulics or pneumatics caissons or simply large controlled injections of water to generate actual waves. However, all of these systems are inefficient in transferring energy to the “wave”, and none of these systems, for various reasons and shortcomings, have yet to come close to generating a wave that replicates the desired size, form, speed and break of the most desirable waves that are sought to be ridden, i.e. waves entering shallow water that plunge, breaking with a tube and which have a relatively long duration and sufficient face for the surfer to maneuver.